1. Field of the Invention
The present invention relates to endoluminal structures. More particularly, the present invention relates to endoluminal stent grafts for use in curved body lumens.
2. Description of the Related Art
A conventional stent graft typically includes a radially expandable stent, formed from a plurality of uniform annular stent springs, and a cylindrical shape graft material to which the stent springs are coupled. Stent grafts are well known for use in reinforcing or holding open the interior wall of a generally tubular shape human vascular and other body lumen.
At deployment, after percutaneous insertion and transluminal transport to the point of use within a damaged or diseased body lumen, e.g., an aneurysmal artery, the stent graft is radially expanded. A stent graft is self-expandable or expandable by application of pressure applied outwardly to the interior portion of the stent graft. After deployment, the stent graft should be somewhat rigid to provide sufficient support to the body lumen.
FIG. 1A is a plan view of stent graft 1, according to the prior art, deployed within a substantially linear segment 10 of a body lumen 6. Stent graft 1 includes a plurality of closely spaced uniform stent springs 2, each formed from a plurality of identical, coupled stent cells 4 into an annular shaped ring around a cylindrical shape stent graft material 3. Within linear segment 10 of body lumen 6, stent graft 1 experienced little or no axial bending force since linear segment 10 of body lumen 6 generally comported with the cylindrical shape of stent graft 1.
However, human luminal systems are tortuous by nature. FIG. 1B is a plan view of stent graft 1, according to the prior art, deployed within a curved segment 11 of body lumen 6. As shown, curved segment 11 includes an interior radius 12.
Within curved segment 11, stent graft 1 is subject to a bending force imposed by curved segment 11 of body lumen 6. Thus, after deployment in a tortuous body lumen, conventional stent grafts were often subjected to significant axial bending and flexing.
It was necessary to limit the amount of axial bending allowed in a deployed stent graft to avoid stent cell overlap at inside radius 12 of curved segment 11 of body lumen 6. Stent cell overlap caused binding or kinking of the stent graft 1 resulting in restriction of flow through the body lumen. Accordingly, the use of conventional stent grafts was limited to certain applications that avoided damage to or destruction of the stent graft from excessive axial bending.